NOTE: the weird thing History tab on MSE says at 2:56pm a trojan by the same name TrojanDownloader:Win32/Carberp.C was removed but 8 min later, at 3:04pm the very same trojan was “Allowed”. Clicking on that just says “Remove this software immediately” but nothing is clickable to do so except the “Get more info about this” which leads to the link below.
After problems with Norton, AVG and McAfee, I removed those and downloaded MSE and Malwarebytes. Both together found 9 trojans and the thing that puzzles me is this. NO OTHER AV found anything! So don’t tell me to get rid of MSE because for my particular laptop it’s the best so far.
This is the trojan:http://www.microsoft.com/security/portal…
TrojanDownloader:Win32/Carberp.C <—-again was removed but 8 min later was allowed!!
NOTE: 2 guys on here spent a lot of time convincing me to download the TSSKiller but WARNING: this is the file that infected my laptop with the worst trojan: a fake antivirus and bogus firewall that completely disabled my computer (browsers crashed, impossible to restart and disabled all my folders/files. This has been removed).

Try going to the MSE Settings and make sure it has NO exceptions listed in its configuration.
The trojan may also know a hole through which it can bypass MSE.
But if you say u want to stick to this AV, just check for NO exceptions in settings, make sure it is updated to the latest version and definitions and do a full scan.
Good luck.